Most of the Christmas light bulb strings achieve their decorative purpose by means of hanging. To enhance their attraction and show their uniqueness, usually the light bulb strings hang on a support frame with special shapes like characters or design patterns. Thus, the light bulb strings display, after being powered, the character or pattern of the support frame. The conventional method uses simply a hanging connection, without effective fixation. That arrangement often leads to loosening. Furthermore, the loosened light bulbs make the pattern or character appear to be incomplete. It is therefore desirable to improve the conventional structure.